# What is tail recursion in Scheme?

## What is tail recursion in Scheme?

Scheme is “properly tail recursive”, meaning that tail calls or recursions from certain contexts do not consume stack space or other resources and can therefore be used on arbitrarily large data or for an arbitrarily long calculation.

How does recursion work in Scheme?

Recursion is a term used to describe a procedure that calls itself, directly or indirectly. In Scheme, simple program repetition/iteration can be achieved via recursion by having a function call itself. Most programs are tail recursive, where the recursive call is the last action that occurs.

### Why is tail recursion An important feature of Scheme?

Tail-recursive functions are important because they can be optimized into loop form: Rather than make a whole new function call, we can simply alter the parameters in memory and jump back to the top of the function.

What is the difference between tail and non tail recursion?

In tail recursion, there is no other operation to perform after executing the recursive function itself; the function can directly return the result of the recursive call. In non-tail recursion, some operations need to be performed using the returned value of the recursive call.

#### How do you define a list in Scheme?

In contrast to Scheme’s unstructured data types, such as symbols and numbers, lists are structures that contain other values as elements. A list is an ordered collection of values. In Scheme, lists can be heterogeneous, in that they may contain different kinds of values.

What are the three laws of recursion algorithm?

Like the robots of Asimov, all recursive algorithms must obey three important laws: A recursive algorithm must call itself, recursively. A recursive algorithm must have a base case. A recursive algorithm must change its state and move toward the base case.

## Why is it called tail recursion?

In computer science, a tail call is a subroutine call performed as the final action of a procedure. If the target of a tail is the same subroutine, the subroutine is said to be tail recursive, which is a special case of direct recursion.

What is tail recursion and non-tail recursion?

### What is map in Scheme?

Map is a built in Scheme function that takes a function and a list as an argument, and returns the list that results by applying that function to every element of the list.

What are closures in Scheme?

Scheme procedure’s aren’t really just pieces of code you can execute; they’re closures. A closure is a procedure that records what environment it was created in. When you call it, that environment is restored before the actual code is executed.

#### What are the four fundamental rules of recursion?

Like the robots of Asimov, all recursive algorithms must obey three important laws:

• A recursive algorithm must call itself, recursively.
• A recursive algorithm must have a base case.
• A recursive algorithm must change its state and move toward the base case.